DE1567691A1 - Process for the production of phosphites - Google Patents

Description

The He find nag concerns tia process offered manufacturing van Phosphines and in particular an improved process for the production of sialkali phosphites, lmali «eoad« re Di-

Dialkaliphoepliit «wtrdea gttfuh & borrowed from orthoposphoric acid, which was obtained by HydroIyso τοα Phoiphortrielilorid, produced. This process has many parts, which include the large working stages that are required to obtain the desired phosphites, i.e. the phosphorus triochloride must first be produced, whereupon it is converted into orthophosphorous acid by hydrolysis, whereupon this acid is neutralized to phosphite wherein the Naeh the Torstehenden method Phosphitprodukte obtained usually require some purification, the S ₉ B. is erslelt by Uakristallisation.

The treatment of τοη graze «phosphorus with a source of hydroxyhones, such as calcium or sodium hydroxide, represents a technical process for the production of τοη hypophosphites. Depending on the reaction conditions used, life-priced products such as phosphite and phosphine result. However, if the Naeh theseA method Vebenprodukt phosphite obtained in smaller amounts t * Comparative de su "

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Hypophosphite yer and must of course τοη dta hypophosphite be separated before it can be used in a normal degree of purity.

It follows from the foregoing that a method sur Production of τοη dialkali phosphites in relatively easier, in a simple and smooth manner as well as in relatir high yields and good purity using τοη white phosphorus as one of the reactants represents a very significant step in this area.

From the German patent specification 877 753 a process for the production of τοη sialkali phosphites by Omaetsung τοη white phosphorus and alkali hydroxides in an aqueous Hediua is known, but temperatures τοη 120 to 140 ⁰ C have to be used, which make working with pressure vessels necessary.

The process of the invention but manufacture τοη Dialkaliphosphiten by reacting τοη white phosphorus and alkali hydroxides in an aqueous medium is characterized gekennseichnet that the reaction τοη at a temperature is carried out for about 50 to 100 ⁰ C, whereby the hydroxide in larger Eonsentrationen than 15 weight-ji Torliegt and the molar ratio τοη hydroxide su phosphorus «is between about 2.5 and about 8.

According to the teachings of the goal of the invention ->. See Bialkaliphosphite in yields up to about 70 to 74 % nmd even higher and in good purity, ie with less than 10% Torhaadenen Hypepaospait impurities. This behavior must be considered great

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unexpected in view of the high yields of obtained Phoephite and the small amounts of the byproducts formed, in particular hypophosphite and phosphate, as is the case with the process according to the invention will.

Xb following is the general reaction equation but ▼ Oil permanent conversion of elemental white phosphorus indicated in phosphite:

(I) P ₄ + 8 OH "+ 4 H ₂ O - * 4 HPO ₅ "" ² + 6 H ₂

where, in the case of a stoehiometric ratio, the OH ~ / P molar ratio is 2. However, complete conversion seldom, if ever, occurs and volatile products such as PH *, P ₂ Hc and the like are usually formed to some extent in the conversion.

In general, any sialkali phosphite can be used by using dt «corresponding alkali hydroxide are produced, for example lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like., wherein Sodium hydroxide and potassium hydroxide due to their lightness Accessibility and cheapness are preferred, of which sodium hydroxide special precaution is taken.

For the implementation according to the present invention are Amounts of alkali hydroxide in the upper part of the stoichiometry Ratio required, i.e. an OH * "/ B molar ratio greater than 2 is necessary, and preferably the OH ~ "/ P molar ratio should be between about 2.5 up to about 8, although molar ratios are also greater than 8 can be used, e.g. molar ratios of 10 and even higher. In addition, the

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Implementation can be carried out in tints of aqueous medium and especially in tints of strongly alkaline aqueous medium, the alkali hydroxide concentration being greater than 15 weights, in which the formation of τοη byphosphite is reduced to a minimum. Although hydroxide concentrations greater than 50 % can be used , btiepitieweite 60% and higher, the berorsugte range of Komientration for the alkali metal hydroxide iwieohen about 25 and about 50 Gtwichtt-jC. Suitable Teaperaturen sur practice of the invention are in the range τοη about 50 to 100 ^ p ₉ even if the eerorlugte temperature range swiechen about 65 ⁰ C and about 100 * C.

In general, the IKmeetiumg can be executed by Weifier Phoephor and a watery lotion of every lufeehlim exercise of the alkali hydroxide can be removed and the Reactants are heated with stirring until dae mitohte photophite product is formed. Da · Dialkalipheephit can be used in lusunge form if desired, or et can be rereohieden from the reaction medium Driving, for example by removing the water, by evaporation of Phoephitt by cooling a relatir Healing, saturated, w & brigen fhoephite solution, crystallization of the Phoephite from a saturated solution Inoculation of the solution, precipitation by adding a · miscible Leaching agent in which the phosphite salts are less soluble, for example methanol, ithanol and the like, and can be won after taking appropriate profits.

A special berorsugtee Terfahren on the extraction of dialkali metal phosphites from the reaction medium consists in the alkali metal hydroxide in greater concentrations than

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about 40 dewiohts-jt and Torsugswelse swisohen about 4-0 and about 50 exceeded i> aasuwenden because dit at the · en Kensentrationen LBsliohkeit of Dialkaliphosphlts and the Dialkaliphosphit crystallized as the reaction progresses, tHe se it au "dsm reaction medium duroh filtratieasmaSaahmea and the like. Be is a really wteentlioker part, since the BialJcalimtallplioepiite from the rtaktioneatdiuB la rtlativ tinfaelitr Veise as well as in rtlatiY pure yem gained. w «rdta köantn, and laiftti-Hol hardly dite lJtlBpieliweiet» u tine «lcoiitiauierliohen Terfaferea iur manufacture of the dialicalipteeepiite be used, while continuously the irietalle from the watery Mtdiua is recovered in the reaction, only

The following example serves as a further explanation of the invention, parts and prosentic statements are not lied to the sewing, unless otherwise indicated.

example

About 100 g of HatriuMJaydrox's solution, as follows, were placed in an animal neck flask equipped with a stirrer, N ₂ inlet, Xheraoaeter, Sasauslafl and a discharge channel, consisting of a lalle and a Tisher-Milligan-daswäsehsr, which is filled with 6N-sulfuric acid specified, introduced. The flask was then _{evacuated under H 2} and phosphorus was introduced. The flask was heated to the specified temperature and the reactants were stirred by operating the stirrer at a specific setting. The results obtained under different experience conditions are summarized in the following table!

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Cons entra
nt IaOH) (HaOH / P)
Molar vertebral
ratio Table I. 8th Products ¹ ^ {%)
HPO ₃ - ² H ₂ PO ₂ ^"1 7.7 Volatile products
PH ₅ , P ₂ H _{4 and} others. Yeraueh
Ir. 15th 4th Temperature time
( ⁰ C) (hrs.) 1 71.1 0.4 21.2 1 30th 4th 100 1 74.0 0.3 25.6 2 50 4th 100 2 72.8 0.4 27.9 3 50 2.5 100 2 50.9 0.2 48.7 4th 50 4th 80 0.75 71.4 0.5 28.4 5 50 8th 80 11.25 72.5 2.9 27.0 6th 30th 4th 80 3 69.9 4.1 27.1 7th 30th 4th 65 1 71.7 0.4 24.2 8th 30th 4th 80 74.0 25.6 9 100

HypQphospAit and Phoapnit were iodoaetron according to the procedure
Jones Jb Swift, Anal. Chem. Volume 25, page 1272 (1953).

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As shown in the table below, can accordingly the teaching of the foolish invention Dinatriuaphosphit from eleaentarea white »phosphorus in relatively high Yields and with alien hypophosphite impurities getting produced.

Sea Toretah example good results were also in the production of other alkali metal phosphites, such as dipotassium phosphite, bilithium phosphite, syrubidium phosphite and the like, and especially in the case of potassium phosphite, obtained under practically the same reaction conditions if the corresponding Hydroxides were used, i.e. potassium hydroxide, Lithium hydroxide, rubidium hydroxide and the like.

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Claims (2)

Claims 1. A process for the preparation of dialkali phosphites by reacting white phosphorus and alkali metal hydroxides in an aqueous medium, characterized in that the reaction "is carried out at a temperature of about 50 to 100 ^° C., the molar ratio of hydroxide to phosphorus being between about 2, 5 and about 8 lies. 2. The method according to claim 1, characterized in that a hydroxide concentration of about 27 to about 50 weight # and preferably from about 40 to about 50 weight percent is employed. I! '". LetlÄQön iAtt. 7 SI Abe. 2 No., 1 Sate 3 d ·· SntlerunB« a-- ν. 4.9-19C7i 009831/131 ^